Explicit dynamics based numerical simulation approach for assessment of impact of relief hole on blast induced deformation pattern in an underground face blast

The exploitation of geo-resources is dominantly done using drilling and blasting. The breakage of rock mass by blasting has many challenges. The optimal breakage in an underground development face/tunnel blast is dependent on the relief area provided to the blast holes. This paper has discussed the impact of the number and diameter of the relief holes on the breakage pattern of the rock. The numerical simulation with varying numbers and diameter of relief hole was carried out for this purpose. The isosurface output from numerical simulation was plotted. The plot was used to compare the extent of deformation under varying conditions of relief holes. The analysis shows that the higher number of relief holes with optimum diameter gives more controlled deformation than single relief hole with larger diameter. The nearfield vibrations were also recorded by placement of seismographs. The waveform analysis of the recorded vibration was carried out. The redesigning of the blasting pattern was done using the results of numerical simulation and waveform analysis. The redesigned pattern consists of four relief holes of 115 mm diameter. It was found that the number of cut blast holes firing simultaneously should not be more than two in order to get the optimum breakage for the modelled condition. The blasting output with the revised design has resulted into the considerable improvements in the pull and reduction of overbreak. The revised pattern has addressed the issues of the socket formation at the site.